The present invention is related to an absorbent material for absorbent articles. More particularly, the present invention is related to an absorbent material fabricated from starch.
Absorbent articles containing an absorbent core, e.g., diapers and sanitary napkins, are widely utilized. In general, such products have an absorbent core which contains one or more layers of fluid absorbent materials, such as fluffed cellulose batt, e.g., wood pulp, cotton fluff, tissue and the like. The absorbent core may additionally contain particles of a superabsorbent. Superabsorbents are hydrocolloids that absorb at least about 10 times its own weight of aqueous fluid. Since superabsorbents are relatively expensive, provide only weak structural integrity and require high surface area to be efficient, they are in general employed as small particulates that are dispersed or imbedded in a matrix of fluffed cellulosic fiber batt, e.g., wood or cotton fluff, or in a thermoplastic foam, e.g., polyurethane foam.
However, these prior art approaches in incorporating a superabsorbent into an absorbent core have disadvantages. For example, superabsorbent particles dispersed in a fluffed cellulosic fiber batt may settle over time, altering the absorption performance and deviating from the designed criteria of the absorbent article. In addition, the fiber batt tends to collapse and close interfiber-capillaries when the batt is expose to liquid, thereby hindering subsequent insults of liquid from having an access to unused portions of the batt and the superabsorbent particles dispersed therein. Furthermore, since superabsorbent particles must be allowed to swell for the particles to efficiently absorb liquid, the collapsed batt which hinders the expansion of the superabsorbent particles prevents efficient use of the particles. An example of such absorbent-hinderance problems is addressed in U.S. Pat. No. 5,147,343 to Kellengerger.
As for dispersing superabsorbent particles in a polyurethane foam, the inherent hydrophobic nature and rigidity of the polyurethane foam cause inefficient use of the absorbent materials. The intercellular structure of the foam may not provide sufficiently large enough space to allow the superabsorbent particles to fully swell, causing an inefficient use of the absorbent capacity of the superabsorbent particles. Moreover, as disclosed for example in U.S. Pat. No. 4,985,467 to Kelly et al., the intercellular structure of the inherently hydrophobic foam must be carefully engineered to allow liquid to have proper access to the imbedded superabsorbent particles.
Consequently, it would be desirable to provide an economical and highly efficient superabsorbent-containing absorbent material that does not have the above-illustrated disadvantages of the prior art absorbent materials.